Blood Shield in of itself is solely based on your health pool, the mastery component is how many Death Strikes it takes to cap said blood shield, now I have no math to back this up but I have found in raiding normals only that 180% unbuffed and 200% unbuffed offered very little if any benefit. Someone much smarter than me probably has done the math though.

Ideally no one has ever hit the level cap of the last expansion, looked at their dungeon blues, and thought "I win."

i personally prefer to just go max out mastery - be the strongest you can be imo.

That's all well and good but if you're maxing out your blood shield (especially on 25H) with any sort of regularity you need to consider dropping some. I am doing 10H and I've found that around 190% unbuffed seems to be enough for me. For reference I went mastery > avoidance > hit

This is a "riposte" build, basically the more avoidance = more crit rating + vengence > more dps and static survival than mastery build.
More survival by having more frequency of death strikes, while boosting your avoidance rather than relying on being hit to heal from the damage % or shield. Our healers don't even parse/log in the top 100 on any fight and I never really find myself taking alot of damage. Yet I can sit around 700k opener for garrosh, 300kish for mid, and end the fight around the same (300kish)

That is way too much haste if you are properly soaking RP with AMS (and regenrative magic glyph) as well as having to tank more than 1 thing from time to time.
I run as low as 1.3k haste (which i cannot get rid of atm) and I am GCD locked 90%+ of the time

EDIT: Also, if you are playing properly (which you should from your progress), Avoidance > Mastery, with hit/exp (7.5%) caps.